Thermal oxidative and aging as an inevitable process in the practical application of road asphalt has great effect on the properties of asphalt. In this paper,the influences of short-term thermal oxidative ageing and ...Thermal oxidative and aging as an inevitable process in the practical application of road asphalt has great effect on the properties of asphalt. In this paper,the influences of short-term thermal oxidative ageing and ultraviolet radiation(UV) aging on the dynamic viscosity,penetration,softening point and rheological properties of two kinds of layered inorganic nano-powder including organo-modified montmorillonite (OMMT) and nanometer brucite (Mg(OH)2) modified asphalts were studied respectively. The rheological properties of these binders have been determined using a dynamic shear rheometer (DSR) through temperatures sweep tests.The rheological and physical analysis showed the two major influences of ageing on the properties for two kinds of layered inorganic nano-powder modified bitumens. On one hand,ageing decreased the viscous behaviors of modified binders,on the other hand,ageing improved the elastic behaviors of modified binders. The performances of binders after aging depended on the combined effect between the modifier and the bitumen. Both the two modifiers resisted the aging of bitumens and the effect of OMMT was better.展开更多
Lacquer is the main raw material of lacquerware,while UV-irradiation is an important factor leading to its aging.In order to investigate the aging behavior of urushi lacquer film under UV-irradiation,and to propose pa...Lacquer is the main raw material of lacquerware,while UV-irradiation is an important factor leading to its aging.In order to investigate the aging behavior of urushi lacquer film under UV-irradiation,and to propose parameters that can be used to evaluate its aging degree,the micro-UV/Py-GC/MS system has been applied in the present work to enrich and identify volatile products released by urushi film during aging on the one hand,and to investigate micro-amount and conventional urushi films with different aging degrees on the other hand,in addition,representative historical samples have also been investigated.Volatile products released by urushi film demonstrate that during UV-irradiation,polysaccharides wrapping urushiol polymer would be first degraded to generate furans and alcohols,and then urushiol polymer would undergo photo-oxidation and break of molecular chain,mainly generating oxidation products including aldehydes,organic acids,and ketones,as well as a small number of alkyl benzenes and hydrocarbons.Py-GC/MS analysis of micro-amount urushi films with different aging degrees indicates that UVirradiation is more destructive to aliphatic chains in urushiol polymer,but it also can accelerate the polymerization of microamount urushi film.Py-GC/MS analysis of conventional urushi films indicates that with the increase of aging degree,the total chromatographic peak area ratio of hydrocarbons to benzene derivatives gradually increases,the peak area ratio of 3-pentadecenyl-catechol to 3-pentadecyl-catechol gradually decreases,and the peak area ratio of aging products of urushiol to 3-pentadecyl-catechol gradually increases.The above parameters were further used to evaluate the aging degree of two urushicontained samples separately collected from the surface and interior of a carved lacquer panel in the Forbidden City,and evaluation results are in accord with the natural aging law and further verify the reliability of the proposed parameters.Research results of the present work can lay a foundation for the in-depth study of the UV-irradiation aging mechanism of urushi.展开更多
Introduction:Prediabetes is a well-established risk factor for type 2 diabetes development.While existing risk prediction models primarily focus on the general adult population,those specifically designed for older ad...Introduction:Prediabetes is a well-established risk factor for type 2 diabetes development.While existing risk prediction models primarily focus on the general adult population,those specifically designed for older adults remain scarce.This study aimed to develop and validate a 3-year risk prediction model for type 2 diabetes specifically for older adults with prediabetes.Methods:Data were derived from the Health Aging Evaluation Longitudinal Survey(HAELS),which included 1,127 older adults with prediabetes defined by FPG between 5.6–7.0 mmol/L at baseline(2019).Incident diabetes was defined as FPG≥7.0 mmol/L at 3-year follow-up(2022).A multivariable Cox proportional hazards regression model with stepwise variable selection was used to identify predictors and construct the prediction model.Bootstrapping was employed for internal validation.Model performance was evaluated using area under the receiver operating characteristic curve(AUC),calibration plots,and decision curve analysis(DCA).A nomogram was constructed to visualize individualized risk.Results:Seven predictors were included in the final model:age,physical activity,waist circumference,baseline FPG,triglycerides,systolic blood pressure,and dessert intake.The model demonstrated good discrimination(AUC=0.752 in the training dataset,0.793 in the validation dataset)and satisfactory calibration.DCA indicated a net clinical benefit within a threshold probability range of 0.02–0.50.Conclusion:This model,demonstrating good predictive performance and clinical utility,provides a simple and practical tool to estimate the 3-year diabetes risk in older adults with prediabetes.展开更多
As a novel chemical marker,methanol has been widely applied to evaluate the ageing state of insulating paper in recent years.Methanol gas sensor(MGS)could be applied to detect the methanol content in transformer oil f...As a novel chemical marker,methanol has been widely applied to evaluate the ageing state of insulating paper in recent years.Methanol gas sensor(MGS)could be applied to detect the methanol content in transformer oil for its high portability and stability.However,it has the defects of a high limit of detection(LOD)and poor anti-interference performance.Therefore,a novel method of detecting methanol in transformer oil based on MGS with the solid-phase extraction(SPE)technology was investigated in this paper.A detection platform for methanol in transformer oil based on SPE was established,and the SPE experimental process and the crucial parameters were optimised.The results show that the SPE decreased the LOD of MGS from 0.4 to 0.2 ppm and effectively eliminated the interfering substances in oil.Although a part of methanol would be lost during the SPE process,the regression correction coefficient was proposed to correct the evaluation errors.The results indicate that the average relative errors decreased from 17.09%to 4.38%,and the proposed method has good applicability.展开更多
基金supported by the 2010 WHUT Ph.D.Candidate Intermational Academic Communication Preresearch Project(Pact No.2010-JL-02)
文摘Thermal oxidative and aging as an inevitable process in the practical application of road asphalt has great effect on the properties of asphalt. In this paper,the influences of short-term thermal oxidative ageing and ultraviolet radiation(UV) aging on the dynamic viscosity,penetration,softening point and rheological properties of two kinds of layered inorganic nano-powder including organo-modified montmorillonite (OMMT) and nanometer brucite (Mg(OH)2) modified asphalts were studied respectively. The rheological properties of these binders have been determined using a dynamic shear rheometer (DSR) through temperatures sweep tests.The rheological and physical analysis showed the two major influences of ageing on the properties for two kinds of layered inorganic nano-powder modified bitumens. On one hand,ageing decreased the viscous behaviors of modified binders,on the other hand,ageing improved the elastic behaviors of modified binders. The performances of binders after aging depended on the combined effect between the modifier and the bitumen. Both the two modifiers resisted the aging of bitumens and the effect of OMMT was better.
基金supported by the National Natural Science Foundation of China(Grant No.21904024)。
文摘Lacquer is the main raw material of lacquerware,while UV-irradiation is an important factor leading to its aging.In order to investigate the aging behavior of urushi lacquer film under UV-irradiation,and to propose parameters that can be used to evaluate its aging degree,the micro-UV/Py-GC/MS system has been applied in the present work to enrich and identify volatile products released by urushi film during aging on the one hand,and to investigate micro-amount and conventional urushi films with different aging degrees on the other hand,in addition,representative historical samples have also been investigated.Volatile products released by urushi film demonstrate that during UV-irradiation,polysaccharides wrapping urushiol polymer would be first degraded to generate furans and alcohols,and then urushiol polymer would undergo photo-oxidation and break of molecular chain,mainly generating oxidation products including aldehydes,organic acids,and ketones,as well as a small number of alkyl benzenes and hydrocarbons.Py-GC/MS analysis of micro-amount urushi films with different aging degrees indicates that UVirradiation is more destructive to aliphatic chains in urushiol polymer,but it also can accelerate the polymerization of microamount urushi film.Py-GC/MS analysis of conventional urushi films indicates that with the increase of aging degree,the total chromatographic peak area ratio of hydrocarbons to benzene derivatives gradually increases,the peak area ratio of 3-pentadecenyl-catechol to 3-pentadecyl-catechol gradually decreases,and the peak area ratio of aging products of urushiol to 3-pentadecyl-catechol gradually increases.The above parameters were further used to evaluate the aging degree of two urushicontained samples separately collected from the surface and interior of a carved lacquer panel in the Forbidden City,and evaluation results are in accord with the natural aging law and further verify the reliability of the proposed parameters.Research results of the present work can lay a foundation for the in-depth study of the UV-irradiation aging mechanism of urushi.
文摘Introduction:Prediabetes is a well-established risk factor for type 2 diabetes development.While existing risk prediction models primarily focus on the general adult population,those specifically designed for older adults remain scarce.This study aimed to develop and validate a 3-year risk prediction model for type 2 diabetes specifically for older adults with prediabetes.Methods:Data were derived from the Health Aging Evaluation Longitudinal Survey(HAELS),which included 1,127 older adults with prediabetes defined by FPG between 5.6–7.0 mmol/L at baseline(2019).Incident diabetes was defined as FPG≥7.0 mmol/L at 3-year follow-up(2022).A multivariable Cox proportional hazards regression model with stepwise variable selection was used to identify predictors and construct the prediction model.Bootstrapping was employed for internal validation.Model performance was evaluated using area under the receiver operating characteristic curve(AUC),calibration plots,and decision curve analysis(DCA).A nomogram was constructed to visualize individualized risk.Results:Seven predictors were included in the final model:age,physical activity,waist circumference,baseline FPG,triglycerides,systolic blood pressure,and dessert intake.The model demonstrated good discrimination(AUC=0.752 in the training dataset,0.793 in the validation dataset)and satisfactory calibration.DCA indicated a net clinical benefit within a threshold probability range of 0.02–0.50.Conclusion:This model,demonstrating good predictive performance and clinical utility,provides a simple and practical tool to estimate the 3-year diabetes risk in older adults with prediabetes.
基金supported by the State Grid Heilongjiang Electric Power Company Ltd.,Electric Power Research Institute Project(52243724000M)the China Postdoctoral Science Foundation(2020M670921)the National Natural Science Foundation of China(52307164).
文摘As a novel chemical marker,methanol has been widely applied to evaluate the ageing state of insulating paper in recent years.Methanol gas sensor(MGS)could be applied to detect the methanol content in transformer oil for its high portability and stability.However,it has the defects of a high limit of detection(LOD)and poor anti-interference performance.Therefore,a novel method of detecting methanol in transformer oil based on MGS with the solid-phase extraction(SPE)technology was investigated in this paper.A detection platform for methanol in transformer oil based on SPE was established,and the SPE experimental process and the crucial parameters were optimised.The results show that the SPE decreased the LOD of MGS from 0.4 to 0.2 ppm and effectively eliminated the interfering substances in oil.Although a part of methanol would be lost during the SPE process,the regression correction coefficient was proposed to correct the evaluation errors.The results indicate that the average relative errors decreased from 17.09%to 4.38%,and the proposed method has good applicability.
